The enhanced processing power of the modern desktop computer has made possible highly sophisticated multimedia presentation systems, wherein various elements such as sound, video and animation are combined for the purposes of entertainment, education, training, and so forth. Such multimedia systems are capable of supporting high-quality visual and audio features such as high-resolution color graphics, including on-screen digital "movies",and stereo sound. Considerable multimedia-based hardware and software products are now available from a wide variety of vendors. QuickTime.TM., for example, Apple Computer Inc.'s multimedia software standard, gives users a way to display, compress, copy and paste time-based data. QuickTime 1.5, introduced last fall, further supports Kodak's Photo CD standard, enabling high-resolution imagery stored on compact disk read-only memory (CD-ROM) to be integrated into the application.
Such multimedia systems are particularly convenient for training and education, since a number of stimuli may be simultaneously presented, thereby enabling a viewer to maximize the intake of information. For example, in one area of the screen animated graphics information may be displayed while, in another area of the screen, a real-time digital movie may be presented. However, even with the multiplicity of audio and visual stimuli made possible by such multimedia presentation systems, it may at times be difficult for an observer to follow along and coordinate the various inputs.
The need exists for an annotation scheme to bridge two or more aspects of a multimedia presentation in order to improve the relationship between them. For example, graphical information in one window may be annotated in time synchronization with an ongoing time-based audio or video program, such as a digital movie occurring in a different window on the same screen. Known animation techniques, such as exclusive-OR raster operations, or the use of a single off-screen buffer, are ineffective, resulting in line drawing with undesirable visual disruption such as "flicker". In order for such multimedia graphical information to be smoothly annotated, a method specifically directed toward the annotation of a graphical image is required, preferably a method that may be easily adapted for synchronization with other audio or visual information, including a digital movie which may be progressing in a different window on the same screen.